Writes UDP data to the buffer - no data is actually sent. Must be wrapped between
beginPacket() initializes the packet of data, it is not sent until
endPacket() is called.
// SYNTAX Udp.write(message); Udp.write(buffer, size);
message: the outgoing message (char)
buffer: an array to send as a series of bytes (byte or char)
size: the length of the buffer
byte: returns the number of characters sent. This does not have to be read